1. Field of the Invention
The present invention relates to an image processing system and a microscope system including the same.
2. Description of the Related Art
In general, an image acquired using a microscope at high magnification has a shallow depth of field. There is known a technique of, for example, acquiring a plurality of microscopic images having different focal planes for a particular sample and combining in-focus images of the plurality of microscopic images, thereby creating an all-in-focus image or a 3D reconstructed image. To select the in-focus images, that is, to determine whether an image is in focus, evaluation based on image contrast can be used.
When creating an all-in-focus image or a 3D reconstructed image, a best-in-focus image is selected from a plurality of images having different focal planes for each position in an image, and the 3D shape of the sample is estimated. After that, optimization processing needs to be performed for the estimated value of the 3D shape. This optimization processing can include reducing estimation errors of isolated points based on the correlation between pixels. The optimization processing can also include estimating the sample shape for a position where the above-described selection cannot be done.
Regarding creation of an all-in-focus image, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-298682 discloses a technique of performing processing using a recovery filter after an all-in-focus image has been created. In general, the image enlargement ratio of the optical system of a microscope is higher than that of the optical system of a digital camera. For this reason, the band of the optical system of the microscope is sometimes not so higher than the sampling band of the image sensor of the camera upon micrography. The band of the optical system can change depending on the numerical aperture, magnification, and the like of the optical system. For example, when the microscope has a zoom optical system, the band of the optical system changes as well. In the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-298682, the coefficient of the recovery filter is determined in accordance with the settings of the optical system, including the magnification and the numerical aperture of the objective lens, in consideration of the change in the band of the optical system.
In general, the image enlargement ratio of the optical system of a microscope is higher than that of the optical system of a digital camera. For this reason, the band of the optical system of the microscope is sometimes not so higher than the sampling band of the image sensor of the camera upon micrography. The band of the optical system can change depending on the numerical aperture, magnification, and the like of the optical system. For example, when the microscope has a zoom optical system, the band of the optical system changes as well.
When evaluating an in-focus state based on the band contrast of an image, the change in the band of the optical system may inhibit accurate in-focus evaluation. An error in the in-focus evaluation based on contrast can occur when contrast based on a factor such as noise not related to the object structure is evaluated because of, for example, application of a high-frequency filter to an image with a low frequency band.
The in-focus evaluation based on contrast is also usable to, for example, acquire height information. The height information acquisition can be used when, for example, object images are captured on a plurality of imaging planes, and an in-focus image at each position is selected from the plurality of images to estimate the height of the object at each position. The height information acquisition can also be used when object images are captured on a plurality of imaging planes, and an in-focus image at each position of the object is selected from the plurality of images, and the selected images are synthesized to create an all-in-focus image.
For example, Jpn. Pat. Appln. KOKAI Publication No. 9-298682 discloses a technique of performing processing using a recovery filter after an all-in-focus image has been created in consideration of a change in the band of the optical system. In this technique, the coefficient of the recovery filter is determined in accordance with the settings of the optical system, including the magnification and the numerical aperture of the objective lens.